In depth

From the previous chapters you already know the principle of how Jet DataModel works. But for a complete understanding, it is a good idea to study the references of all the classes that make up Jet DataModel.

Basic classes

These are the classes from which the entities - the data models of your application - must inherit.

Class	Meaning of
Jet\DataModel	The most basic abstract class from which other classes inherit. The main entities of the application must inherit from this class.
Jet\DataModel_Related	Generic abstract class of all subentities in any internal session to the main entity. No subentity within an application should directly inherit from this class.
Jet\DataModel_Related_1toN	Abstract class from which inherits application subentities that are bound to the parent entity by internal relations of type 1:N.
Jet\DataModel_Related_1to1	Abstract class from which inherits application subentities that are bound to the parent entity by internal relations of type 1:1.

Definition - models (entities)

The following classes represent class definitions (i.e. class attributes converted into object form).

Class	Meaning of
Jet\DataModel_Definition	Basic class for working with definitions
Jet\DataModel_Definition_Model	The base abstract class common to other classes defining entities and subentities.
Jet\DataModel_Definition_Model_Main	The class defining the main entity.
Jet\DataModel_Definition_Model_Related	Abstract class defining all types of subentities.
Jet\DataModel_Definition_Model_Related_1to1	A class defining subentity that is in a 1:1 relation to the parent.
Jet\DataModel_Definition_Model_Related_1toN	Class defining a subentity that is in a 1:N relation to the parent.

Definition - properties

The following classes represent class property definitions (that is, class property attributes converted to object form).

Class	Meaning of
Jet\DataModel_Definition_Property	The base abstract class common to all property types.
Jet\DataModel_Definition_Property_Id	Represents the type DataModel::TYPE_ID
Jet\DataModel_Definition_Property_IdAutoIncrement	Represents the DataModel::TYPE_ID_AUTOINCREMENT type
Jet\DataModel_Definition_Property_String	Represents the DataModel::TYPE_STRING type
Jet\DataModel_Definition_Property_Bool	Represents the DataModel::TYPE_BOOL type
Jet\DataModel_Definition_Property_Int	Represents the DataModel::TYPE_INT type
Jet\DataModel_Definition_Property_Float	Represents the DataModel::TYPE_FLOAT type
Jet\DataModel_Definition_Property_Locale	Represents the DataModel::TYPE_LOCALE type
Jet\DataModel_Definition_Property_Date	Represents the DataModel::TYPE_DATE type
Jet\DataModel_Definition_Property_DateTime	Represents the DataModel::TYPE_DATE_TIME type
Jet\DataModel_Definition_Property_CustomData	Represents the DataModel::TYPE_CUSTOM_DATA type
Jet\DataModel_Definition_Property_DataModel	Represents the DataModel::TYPE_DATA_MODEL type - that is, the relation to the subentity.

Composite keys

Class	Meaning of
Jet\DataModel_Definition_Key	It represents the definition of a coposite key.

Relations

The Jet DataModel keeps together information about internal and external relations so that it can use them efficiently. Thus, the following classes are intended primarily for internal Jet DataModel needs.

Class	Meaning of
Jet\DataModel_Relations	A base class whose primary purpose is to record and hold information about all known relations.
Jet\DataModel_Definition_Relation	A base abstract class representing a general relation.
Jet\DataModel_Definition_Relation_Internal	The class represents the definition of an internal relation.
Jet\DataModel_Definition_Relation_External	The class represents the definition of the external relation.
Jet\DataModel_Definition_Relation_Join_Item	Defines a specific link between two properties.
Jet\DataModel_Definition_Relation_Join_Condition	Defines the relationship between a property and a specific value.

ID controllers

Of course, the list of controller IDs must not be missing.

Class	Meaning of
Jet\DataModel_IDController	General abstract class common for all ID controllers.
Jet\DataModel_IDController_AutoIncrement	ID controller operating with a numeric sequence generated by a relational database.
Jet\DataModel_IDController_UniqueString	ID controller generating a random text string with a timestamp at the beginning.
Jet\DataModel_IDController_Passive	A passive ID checker that relies on the application logic to set the identification properties.

Restricted recording mode

Within loading data, it is possible to limit the upload range by rules. The rules are of course converted to an object.

Class	Meaning of
Jet\DataModel_PropertyFilter	Represents the load range rules (i.e. what can be loaded) in limited upload mode.

Queries

The following classes together form the query definition. Both queries of the SELECT type, i.e. the complete definition of what the database should retrieve, and queries from which only the WHERE part is used, i.e. for DELETE and UPDATE operations.

Class	Meaning of
Jet\DataModel_Query	Base class whose instance represents an abstraction of the SQL query.
Jet\DataModel_Query_Select	Represents a list of columns to load for a SELECT query.
Jet\DataModel_Query_Select_Item	Represents a specific column within the list for loading in a SELECT query.
Jet\DataModel_Query_Select_Item_Expression	It represents, for example, calling a SQL function within a list to load it in a SELECT query.
Jet\DataModel_Query_Where	Represents the entire WHERE part of all SQL queries.
Jet\DataModel_Query_Where_Expression	Represents a specific part of the WHERE part of the SQL query. That is, a binding to a column (or part of SELECT), an operator and a value.
Jet\DataModel_Query_Having	Represents the entire HAVING part of SQL queries of the SELECT type.
Jet\DataModel_Query_Having_Expression	Represents a specific part of the HAVING portion of the SQL query. That is, the binding to the column (or SELECT part), operator and value.
Jet\DataModel_Query_GroupBy	Represents the definition of the GROUP BY part of SQL queries of the SELECT type
Jet\DataModel_Query_OrderBy	Represents the definition of the ORDER BY part of SQL queries of the SELECT type
Jet\DataModel_Query_OrderBy_Item	This is a specific element in the ORDER BY part of the SQL query.

Loading - iterators

In the context of loading, we talked about iterators for special data loading mode. Here they are:

Class	Meaning of
Jet\DataModel_Fetch	The base abstract class common to both iterators.
Jet\DataModel_Fetch_Instances	Iterator for retrieving a list of entity instances.
Jet\DataModel_Fetch_IDs	Iterator for retrieving a list of entity identifiers.

Data modification

When Jet performs data storage - i.e. writes to the database (either by INSERT or UPDATE), it passes a set of data to the backend for modification in the form of instances of the following classes.

Class	Meaning of
Jet\DataModel_RecordData	A class represents the entire set of data to be stored.
Jet\DataModel_RecordData_Item	A specific item in the data set to be stored.

Backend

Class	Meaning of
Jet\DataModel_Backend	The base abstract class common to all backends.
Jet\DataModel_Backend_Config	The base abstract class defining configuration common to all backends.

Helper

The utility is designed for creating tables and updating them, or for displaying SQL queries intended for performing these operations. However, the helper is nothing more than a small facade, calling backend instances and the corresponding methods.

Class	Meaning of
Jet\DataModel_Helper	Facade calling backend methods designed to create and update DB tables based on definitions.